The present invention relates to fluid controls for electrical circuits, more particularly pneumatic controls for electrical signal circuits, for example of the type found in gasoline service stations, in which hoses are laid across the traffic lanes. A vehicle crossing the hose momentarily compresses the hose and sends a brief pneumatic pulse to a device for closing a signal circuit to cause, for example, an audible signal such as the ringing of a bell.
Such devices, however, have the disadvantage that they actuate the bell every time the hose is compressed. Thus, a vehicle entering a service station will actuate the bell twice, at an interval depending on the speed of the vehicle. Similarly, a vehicle leaving the station will actuate the bell twice. In fact, however, it is useful to the service station operator that only one signal be given, namely, when the vehicle enters the station. It is undesirable that a signal be given when the vehicle leaves the station; for if the operator is in the rear of the station and cannot see the area of the gas pumps, then he cannot tell by listening, whether there is a vehicle entering the station or a vehicle leaving the station. If a vehicle is merely leaving the station, then he need not come forward to offer services. Moreover, if an entering vehicle crosses the hose slowly, then the interval between the two signals may confuse the operator into believing that two vehicles have in fact entered, or one vehicle entered and one left, etc. In short, in the case of two-axled vehicles, there is approximately four times as much bell ringing in a service station as there need be, with the result that the operator spends a great deal of time answering what amounts to false alarms.
Accordingly, it is an object of the present invention to provide a pneumatic control for an electrical circuit, with means selectively to disable the operation of the control, whereby under certain circumstances the electrical circuit will be opened or closed, and under other circumstances will not.
Another object of the present invention is the provision of a pneumatic control for an electrical circuit, which is operative when compressive pressure is exerted from one direction and inoperative when compressive pressure is exerted from the opposite direction.
Still another object of the present invention is the provision of a pneumatic control for an electrical circuit, which cannot be actuated more than once in a given period of time.
A further object of the present invention is the provision of a pneumatic control for a signal circuit, in which a signal is given only under preselected conditions.
Finally, it is an object of the present invention to provide a pneumatic control for an electrical circuit, which will be relatively simple and inexpensive to manufacture, easy to install, adjust, maintain and repair, and rugged and durable in use.
Although the present application speaks broadly of electrical circuits, the preferred electrical circuit is a signal circuit, and the preferred signal is an audible signal such as a bell. At the same time, it will be recognized that the present invention is easily applicable to the control of a plurality of other types of electrical circuits.